The architecture of high-performance Internet routers has advanced in the last several years to provide increased performance in routing ever-greater volumes of network traffic. It is not uncommon for a router to support numerous protocols as well as several control applications for configuration and maintenance of the router tables, protocols, and network policies. These advances have increased the complexity of the router such that the efficient management of the router's configuration is critical for reliable network performance.
The configuration of a router is typically managed by a centralized system configuration database residing on the router. The contents of the configuration database control the operation of the router, and manipulation of the contents of the configuration database are accomplished using a management interface, such as a command line interface (CLI). In a traditional router architecture, the CLI has full access to the system configuration database through a configuration manager process, and is intended to be the primary method of access for system professionals. The CLI can be used not only for configuration commands, but also for other interactive commands that control the operation of the router, e.g. commands to start up or shut down specific applications or processes.
Another commonly used management interface to the configuration of the router is the Simple Network Management Protocol (SNMP). SNMP is a protocol that governs network management and monitoring of network devices and their functions and is documented in Request For Comment (RFC) 2570, Introduction to Version 3 of the Internet-Standard Network Management Framework, authored by the Network Working Group of the Internet Engineering Task Force (IETF), and published by the Internet Society in April, 1999. Yet another more recently developed management interface to the configuration database of the router is based on the Extensible Markup Language, or XML. An XML-based network management interface typically uses XML to encode communication data that was entered by a network administrator via a graphical user interface (GUI), and provides a mechanism for transmitting the complex data that is used to manage networking devices to the configuration database.
It is not uncommon for certain applications and protocols on a router to allow access to their corresponding configuration data by all three of the above-described network management interfaces—CLI, SNMP, and XML. In fact, a network administrator could enter different CLI or SNMP commands that accomplish the identical configuration change on a given router. Maintaining the router to recognize all of the different management interface commands for all of the various applications and protocols that the router supports can be difficult, requiring numerous updates to data such as SNMP management information base (MIB) definitions, CLI command trees, or XML tags.
In existing router management technology, the logic to support the applications, protocols, and associated management interfaces are centrally managed in a single master program. This can result in a single point of failure, meaning that even if there is a problem with only one protocol or application or interface, the entire program could crash, bringing the router down with it. In addition, if the master program needs to be updated, say to accommodate a new protocol, e.g. the Multi-Protocol Label Switching (MPLS) protocol, or to accommodate a new faster blade, either of which can introduce a new set of CLI commands, SNMP requests, or XML accesses that must be supported, then the master program must be brought down in order to perform the updates, thereby temporarily taking the router out of service.
In an effort to overcome some of the limitations in existing router management technology, separate processing entities known as master agents and subagents have been developed in the context of the SNMP management framework. A master agent sends and receives the SNMP requests but has little or no access to the management information, e.g. the MIB data in the configuration database. The subagent does have access to the management information and processes the SNMP requests, but is shielded from the SNMP requests themselves. RFC 2741, Agent Extensibility (AgentX) Protocol, authored by the Network Working Group of the IETF, and published by the Internet Society in January 2000, documents the concept of extensible SNMP agents and a protocol for communication between the master agent and the subagent.
The SNMP master agent/subagent technology has provided new opportunities for improving configuration management. However, little has been done to overcome the limitations in existing router management technology in the context of other management interfaces, or to provide a comprehensive solution to configuration management regardless of management interface.